I was browsing thorugh a few reddit pages when I happen to came upon this Askreddit post:
Now, this subreddit is just full of good questions but this particular one is attention-grabbing so I decided to read through it. As expected, most of the replies are the usual "I asked for an autograph and he/she declined so he/she's a bitchy shit" shit. It's hard work to actually read legit sounding experiences with mean celebrities, without all the drama of being scorned by someone famous.
To sum them all up, Demi Lovato, Julia Roberts, and Anne Hathaway are apparently mean girls in real life. Lindsay Lohan is said to be bitchy too but her weirdness is more noteworthy, so it's not really clear which is the real thing. The most surprising I read about was Micheal Jordan is the default Horrible Dick in Real Life. Oh and that Rachel Ray "is a terrible human being".
In the neutral side, Emma Watson is extremely introverted/shy and Mariah Carrey is (not surprised here) is a total diva.
On the brighter side, Adam Sandler, Kim Kardashian, Selena Gomez, John Mayer, Ben Affleck and Jennifer Garner, Taylor Swift, Mila Kunis, James Franco,Sarah Michelle Gellar, Alec Baldwin, Joseph Gordon Levitt, Jeff Bridges, Dywane Johnson, Robin Williams are are ultra nice guys.
Last but not the least, Keanu Reeves is a saint.
Well, these are not my experiences or opinions, it could be a full decade before I could even meet a Hollywood celebrity in person.
So to read how various experiences formed into conclusions, read the rest of the thread here.